NEW YORK (Reuters Health) - Perinephric fat assessment may help predict problems following major liver surgery, suggests a new study.

Outer abdominal fat, however, appears to be less important.

Any major operation comes with a range of possible complications, and how long patients stay at the hospital varies accordingly, said Dr. Yuman Fong of Memorial Sloan-Kettering Cancer Center in New York City, who led the study.

To determine how much added risk might come with extra weight, and whether or not the location of that fat matters, Dr. Fong and his team studied nearly 350 patients undergoing major hepatic operations 1996 and 2001.

Within 30 days of the surgery, two out of three patients suffered complications and nine died, according to the report published online November 15th in Archives of Surgery. The average patient stayed about 11 days in the hospital.

The more perinephric fat a patient (as a marker of intra-abdominal fat) - as determined by computed tomography -- the greater the risk of complications, fatal or not, and the longer the hospital stay.

Body mass index and outer belly fat were not linked to such problems, however.

Based on other data collected by his team, Dr. Fong said his findings may be relevant to other abdominal surgeries as well.

According to the researchers, gauging the amount of fat doesn't require much extra work, because most patients being considered for abdominal surgery will have a CT scan done anyway.

"Any surgeon in less than a second can glean the information," said Dr. Fong.

So the measurement would usually be available without adding extra cost, Dr. Robert Rege of the University of Texas Southwestern Medical Center, in Dallas, told Reuters Health in an e-mail.

"It is not clear if it would be medically or economically reasonable to order a CT scan simply to make the measurement for risk assessment alone," added Dr. Rege, who also wrote a commentary in the journal.

To be practical in any surgical setting, Dr. Rege suggested that more data are needed to determine how different amounts of organ fat affect outcomes.

"It would be optimal if there were interventions (during surgery) that could decrease the risk in those patients who were determined to have high risk by the measurement," he said.